1. Field of the Invention
This invention relates generally to recharging an electric storage battery using a charger and a wall outlet. More particularly, the invention pertains to detecting the current rating of a circuit that supplies power to the charger and battery.
2. Description of the Prior Art
A hybrid vehicle is a vehicle that uses two distinct power sources, such as an on-board rechargeable energy storage system and a fueled power source for vehicle propulsion. The term hybrid vehicle most commonly refers to hybrid-electric vehicle (HEV), which use internal combustion engines and electric batteries to power electric motors. Generally, kinetic energy of the vehicle is recovered during braking, converted to electric energy and stored in one of the batteries.
A plug-in hybrid electric vehicle (PHEV) is a hybrid, which has additional battery capacity and the ability to be recharged from an external electrical outlet supplied by a public utility power grid. The vehicle can be used for short trips of moderate speed without needing the internal combustion engine (ICE) component of the vehicle's power train, thereby saving fuel costs. In this mode of operation, the vehicle operates as a pure battery electric vehicle, but the long range and additional power of the ICE power train is available when needed. PHEVs are commonly called “grid-connected hybrids.”
PHEVs require the user of a battery charging system to plug a vehicle charger into an AC outlet. But the wall outlets and circuits that provide 110V and 220V AC to a user of a battery charging system have various current rating and other operating parameters that affect the rate at which the battery can be charged. To charge the vehicle's battery it is desirable to draw the maximum continuous current at which the circuit is rated.
When a circuit distribution panel, wire and outlet are installed in a building, the outlet is selected so that its rating is compatible with the current rating of the wire and circuit distribution panel. Later if a connection is made between a PHEV charger and the outlet, without knowledge of the current rating of the outlet, the charger will be limited by code to draw the magnitude of current permitted in the lowest rated outlet, which is typically 15 A. This reduction in current draw will unnecessarily reduce the power draw from a higher current outlet and extend the length of the period required to charge the traction battery.
To overcome this difficulty, there is a need in the industry accurately and reliably to detect the current rating of the electrical power supply circuit, to communicate that current rating to the battery charger, and to adjust the charge rate such that the length of charge period is minimized.